System for an internal combustion engine with an electric torque assist

The present subject matter is related to internal combustion (IC) engines in general, and in particular with an implementation of an electric torque assist in the IC engines to provide inertial compensation for reducing mass-based inertial components added to a 2 stroke or 4 strokes IC engines. Furthermore, the disclosed subject matter includes a method for providing electric torque assist to overcome crankshaft speed variation over strokes during engine operation, thereby overcoming a speed variation problem caused by the engine's lower inertia at low and idle speeds.

Conventionally, a 2-stroke or 4-stroke Internal Combustion (IC) engines have only one stroke of two strokes or four strokes, respectively, providing enough power to keep the IC engine running. The two strokes in the 2-stroke engine are referred to as a “compression stroke,” when an air-fuel mixture is compressed, and a “power stroke,” when an ignited compressed air-fuel mixture provides a large downward force to a piston assembly, providing power to the engine. The power impulse is thus generated during one of the two strokes, and the crankshaft rotates one revolution during the two strokes, with a 180-degree rotation in each stroke. In the 4-stroke engine, there are four strokes including a suction stroke, a compression stroke, a power stroke, and an exhaust stroke, where two strokes make a 360-degree rotation of the crankshaft, and the power stroke provides the power to the engine.

In both types of the engines, the compression stroke energy demand is high in order to compress the air-fuel mixture to a high degree, allowing the mixture to ignite in a subsequent power stroke, with the power stroke beginning at a Top Dead Centre (TDC) and ending at a Bottom Dead Centre (BDC), covering a 180-degree rotation of the crankshaft during this power stroke.

To ensure that the subsequent compression stroke can compress the air-fuel mixture, every internal combustion (IC) engine has an intertrial block made an integral part of the crankshaft or provided as a flywheel component attached to the crankshaft so that the energy needs of the compression stroke are met from the stored energy of the inertial block, with the energy of the inertial block augmented during the power stroke by the ignition of the air-fuel mixture. Any reduction in inertial block mass results in a large speed swing during the compression stroke, with this swing being more pronounced at low and idling speeds of the internal combustion (IC) engine.

For instance,illustrates an exemplary schematic view of an Internal Combustion (IC) engine assembly with an Integrated Starter Generator (ISG)connected to a crankshaft and an inertial mass provision made as part of the crankshaft for speed optimization in conventional internal combustion (IC) engine according to the prior art. The Internal Combustion (IC) engine with the integrated starter generator (ISG)is mounted on the crankshaft. The conventional system includes, in general, an internal combustion (IC) engine assemblyincluding a piston assemblyincluding a fuel-air mixture into a confined spacefor ignition at a Top Dead Centre (TDC) positionduring the upward stroke (i.e the compression stroke). A crankshaft assembly, which includes a necessary inertial mass attached for maintaining necessary rotational in the conventional internal combustion (IC) engine, is coupled to the integrated starter generator (ISG)mounted on the crankshaft as illustrated in a shaft representation. The piston assemblymoves with every stroke between the Top Dead Centre (TDC)and the Bottom Dead Centre (BDC), and two such reciprocating strokes make one 360-degree rotational revolution of the crankshaft assembly. With the integrated starter generator (ISG)connected to the crankshaft assembly, the integrated starter generator (ISG)also makes one revolution during one revolution of the crankshaft assembly.

Therefore, there is a need to address the aforementioned technical draw backs and problems in a speed variation problem associated with the engine's lower inertia at low and idle speed operation of the engine.

In view of the foregoing, an embodiment of the present invention provides a configuration in which the above problem of crankshaft speed variation due to reduced inertial mass is overcome by using an Integrated Starter Generator (ISG), specifically in the motoring mode (M) with electric torque assist during the appropriate stroke, thus meeting the speed shortfall in the crankshaft speed throughout the appropriate stroke of both 2-stroke and 4-stroke engines, during idling and low-speed operation. With lower inertial mass and overall engine weight, it is thus feasible to provide speed variation regulation at low and idling speeds. Furthermore, this allows the engine to run on a lean fuel-air mixture, which improves emissions at low and idling speeds.

In an aspect, a system for an internal combustion (IC) engine with an electric torque assist is provided. The system includes a crankshaft assembly of the IC engine, a piston assembly, an integrated starter generator (ISG), a sensing assembly, a MOSFET bridge, a MOSFET driver, a battery and a pulsar coil, and a control unit. The piston assembly is connected with the crankshaft assembly of the IC engine. The integrated starter generator is connected to a side of the crankshaft assembly of the IC engine using a shaft. The ISG operates in any of a motoring mode (M) or a generation mode (G). The sensing assembly is mounted internally or externally between the crankshaft assembly and the ISG of the IC engine. The sensing assembly provides a stream of pulses proportional to an instantaneous speed of the crankshaft assembly and generates pulses with respect to the position of the piston assembly. The MOSFET bridge is connected to the ISG. The MOSFET bridge enables the motoring mode (M) or the generation mode (G) of the ISG. The MOSFET driver is connected to the MOSFET bridge and is configured to switch operations of the MOSFET bridge during electric torque assist to the motoring mode (M) or the generation mode (G). The control unit includes a controller or a processor that is configured to determine the instantaneous speed of the crankshaft assembly using the stream of pulses from the sensing assembly, compute the pulses from the sensing assembly into one or more engine cycle phases, monitor the instantaneous speed of the crankshaft assembly and speed shortfall in the IC engine, determine a target value for the electric torque assist by analysing the speed shortfall and the instantaneous speed of the crankshaft assmly, or detecting the position of piston assembly by the sensing assembly, when the instantaneous speed of the crankshaft assembly is less than a predefined threshold speed value of the IC engine, and provide the electric torque assist to the ISG by switching the MOSFET bridge to the motoring mode (M) of the ISG using the MOSFET driver to maintain an optimum electric torque assit throughout the one or more engine cycle phases.

In some embodiments, the IC engine comprises a 2-stroke engine or a 4-stroke engine.

In some embodiments, the controller or the processor is configured to switch the MOSFET bridge to the generation mode (G) of the ISG when the instanteous speed of the crankshaft assembly is greater or equal to the predefined threshold speed value of the IC engine.

In some embodiments, the one or more engine cycle phases for the 4 stroke engine includes a suction stroke, a compression stroke, a power stroke, and an exhaust stroke. The one or more engine cycles phases for the 2 stroke engine includes a suction/compression stroke and a power/exhaust stroke.

In some embodiments, the sensing assembly is mounted externally to the ISG of the IC engine to include one or more sensors. The one or more sensors include magnetic pick-up coils, Hall-effect sensors, magneto-resistive element (MRE) sensors, and optical sensors.

In some embodiments, the sensing assembly is mounted internally to the ISG of the IC engine to determine the stream of pulses. The stream of pulses can be detected with the control unit using any of back EMF measurement, zero-crossing detection or current sensing.

In some embodiments, the one or more engine cycle phases can be detected using the pulsar coil.

In as aspect, an embodiment herein provides a method for an internal combustion (IC) engine with electric torque assist. The method includes providing a stream of pulses proportional to an instantaneous speed of a crankshaft assembly and a position of a piston assembly reaching a Top Dead Center (TDC) of the IC engine when it is running using a sensing assembly. The method includes determining the instantaneous speed of the crankshaft assembly using the stream of pulses from the sensing assembly using a control unit. The method includes computing the pulses from the sensing assembly into one or more engine cycle phases including a suction stroke, a compression stroke, a power stroke, and an exhaust stroke, using the control unit. The method includes monitoring the instantaneous speed of the crankshaft assembly and speed shortfall in the IC engine using the control unit. The method includes determining a target value for the electric torque assist by analysing the speed shortfall and the instantaneous speed of the crankshaft assembly or detecting the position of piston assembly by the sensing assembly, when the instantaneous speed of the crankshaft assembly is less than a pre-defined threshold speed value of the IC engine, using the control unit. The method includes providing the torque-assist to an ISG by switching a MOSFET bridge to a motoring mode (M) of the ISG using a MOSFET driver to maintain an optimum torque-assist throughout the one or more engine cycle phases using the control unit. The method includes switching the ISG in a generation mode (M) using the MOSFET bridge when the instanteous speed of the crankshaft assembly is greater or equal to the predefined threshold speed value of the IC engine.

The electric torque, which compensates for the lower inertia of the engine mechanical components, leads to enhanced emission control of the IC engine. Engines define a driving cycle that begins with the engine idling by default. The engine will be cool at this point, and frictional forces will be relatively high. To overcome frictional forces and keep the engine running without shutting it down, extra fuel is fed into the engine to increase power, which makes the air-fuel mixture rich, which increases emissions. Closed-loop control of the air-fuel mixture is disabled during this time. Closed-loop control is enabled only when the engine temperature reaches a certain threshold or other vehicle requirements are met. This means that in a conventional system, emissions are intentionally higher at the start until closed-loop stoichiometric ratio control is implemented. This limitation is overcomed by this system with the electric torque-assist.

The present invention emphasizes the necessity of employing an integrated starter generator (ISG) for electric torque assistance on specific strokes of a 2-stroke or 4-stroke Internal Combustion (IC) engine with reduced inertial mass for speed optimization at low and idle speeds.

With reference to the following description, these and other aspects of the current subject matter will be better understood. This summary is provided to introduce a selection of concepts in a simplified form, in accordance with one embodiment of the present subject matter. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the claimed subject matter's scope.

The embodiments described herein, and their various features and advantageous details, are explained in considerable detail with reference to the non-limiting embodiments illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted to avoid obscuring the embodiments described herein. The examples provided herein are provided solely to facilitate an understanding of how the embodiments described herein may be practiced and to further enable those skilled in the art to practice the embodiments described herein. As a consequence, the examples should not be interpreted as limiting the scope of the embodiments described herein.

As aforementioned, there is a need for an approach that employs an Integrated Starter Generator (ISG) for electric torque assistance on specific strokes of a 2-stroke or 4-stroke Internal Combustion (IC) engine with reduced inertial mass for speed optimization, thereby overcoming a speed variation problem caused by the engine's lower inertia at low and idle speeds. Referring now to the drawings, and more particularly to, where similar reference characters consistently represent corresponding aspects throughout the figures, preferred embodiments are illustrated.

illustrates a schematic diagram of four strokes of a 4-stroke Internal Combustion (IC) engine and energy needs of each stroke according to some embodiments herein. The energy needs of each stroke are included with positive and negative markings during each stroke, where a positive sign indicates energy added to a rotational mass and a negative sign indicates implying energy used from the rotational mass as the Internal Combustion (IC) engine rotates. A four-stroke engine with the four-stroke Internal Combustion (IC) engine takes a representative form. A piston movementis between a Top Dead Centre (TDC) and a Bottom Dead Centre (BDC) during each of the strokes. An intake stroke or a suction strokedoes not provide power to the Internal Combustion (IC) engine. On the contrary, this movement uses the inertial energy of the rotating crankshaft assembly. During this stroke, the energy useis a negative sign, signifying this inertial use. During the compression stroke, the inertial energy of the crankshaft assembly is used, and this use are larger than the use in the suction strokeas the air-fuel mixture is under compression in the Top Dead Centre (TDC) space. In some embodiments, the Top Dead Centre (TDC) is a confined space. An electric torque assistance is provided to the Internal Combustion (IC) engine during the compression stroke, that allows reduction of a mass of rotational inertial parts provided in the Internal Combustion (IC) engine and making up for this with the electric torque assist.

During the next stroke i.e. a power stroke, the fuel-air ignition provides energy to the crankshaft assembly, as illustrated by the positive sign in the energy sign representation. The final stroke is an exhaust stroke, where the crankshaft assembly uses the inertial energy to scavenge the products of ignition in the power stroke. In some embodiments, the exhaust strokeuses the inertial energy of the crankshaft assembly. The integrated starter generator (ISG) is moved to a motoring mode (M) and electric torque assist is provided to the crankshaft assembly in the compression stroke, and the integrated starter generator (ISG) is moved back to a generation mode (G) during the three remaining strokes: the suction stroke, the power stroke, and the exhaust stroke, to charge a battery system. In some embodiments, as the integrated starter generator (ISG) is rapidly switched between the motoring mode (M) and the generation mode (G), it enables a feasibility of preferentially using the electric torque assist mode during any of the two other strokes i.e. the suction strokeand the exhaust stroke. These two strokes are net inertial energy consumers from the crankshaft assembly. The use of the two different modes, namely the motoring mode (M) and the generation mode (G) of the Integrated Starter Generator (ISG), is switched during the beginning of the stroke and the end of the stroke as located by the Top Dead Centre (TDC) position and the Bottom Dead Centre (BDC) position.

illustrates a block diagram of a systemfor an internal combustion (IC) engine for controlling an Integrated Starter Generator (ISG)with an electric torque assist according to some embodiments herein. The systemfor the internal combustion (IC) engine with electric torque assist includes a crankshaft assembly, a piston assembly, the ISG, a sensing assembly, a MOSFET bridge, a MOSFET driver, a battery) and a pulsar coil, and a control unit. The crankshaft assemblyof the IC engine is the assembly with reduced inertial mass. The IC engine may be any of a 2-stroke engine or a 4-stroke engine. The piston assembly (not shown in) is connected with the crankshaft assemblyof the IC engine. The integrated starter generator (ISG)is connected to a side of the crankshaft assemblyof the IC engine using a shaft. The ISG is configured to operate in any of a motoring mode (M) or a generation mode (G). The sensing assemblyis mounted internally or externally between the crankshaft assemblyand the ISGof the IC engine. The sensing assembly is configured to provide a stream of pulses proportional to an instantaneous speed of the crankshaft assemblyand generate pulses with respect to the position of the piston assembly. The sensing assemblymay be mounted externally to the ISGof the IC engine to include one or more sensors. In some embodiments, the one or more sensors include magnetic pick-up coils, Hall-effect sensors, magneto-resistive element (MRE) sensors, optical sensors, and the like. The sensing assemblymay be mounted internally to the ISGof the IC engine to determine the stream of pulses. In some embodiments, the stream of pulses can be detected with control unitusing any of back EMF measurement, zero-crossing detection, or current sensing, and the like.

The MOSFET bridgeis connected to the ISGand enables the motoring mode (M) or the generation mode (G) of the ISG. The MOSFET driveris connected to the MOSFET bridgeand is configured to switch operations of the MOSFET bridgeduring torque-assist to the motoring mode (M) or the generation mode (G). The control unitincludes a controller or a processor that is configured to (i) determine the instantaneous speed of the crankshaft assemblyusing the stream of pulses from the sensing assembly, (ii) compute the pulses from the sensing assemblyinto one or more engine cycle phases, (iii) monitor the instantaneous speed of the crankshaft assemblyand speed shortfall in the IC engine, (iv) determine a target value for the torque-assist by analyzing the speed shortfall and the instantaneous speed of the crankshaft assemblyor detect the position of piston assembly by the sensing assembly, when the instantaneous speed of the crankshaft assemblyis less than a predefined threshold speed value fo the IC engine, and (v) provide the electric torque assist to the ISGby switching the MOSFET bridgeto the motoring mode (M) of the ISGusing the MOSFET driverto maintain an optimum torque-assist throughout the one or more engine cycle phases. The one or more engine cycle phases for the 4-stroke engine may include a suction stroke, a compression stroke, a power stroke, and an exhaust stroke. The one or more engine cycle phases for the 2-stroke engine may include a suction/compression stroke and a power/exhaust stroke. The one or more engine cycle phases may be detected using the pulsar coil.

In some embodiments, the controller or the processor is configured to switch the MOSFET bridgeto the generation mode (G) of the ISG, when the instantaneous speed of the crankshaft assemblyis greater than or equal to the predefined threshold speed value of the IC engine. In some embodiments, the controller or the processor is configured to monitor energy consumption and state of charge (SOC) of the battery) when the ISGis in the motoring mode (M).

The sensing assemblyresolves the position of the crank with respect to the Top Dead Centre (TDC) and the Bottom Dead Centre (BDC) and enables the control unitto switch the operations of the MOSFET bridgeto the motoring mode (M) or the generation mode (G). The MOSFET bridgeis typically 3 half-bridges, as in the case of a three-phase integrated starter generator (ISG). The MOSFET bridgethrough the MOSFET driverensures a dual-direction energy flow between the ISGand the battery, where the batteryis enclosed with a vehicle-mounted battery system. The MOSFET is connected using power cables and a protective schemeon top of the vehicle-mounted battery system and a similar arrangementbetween the ISGand the MOSFET bridge. During the electric torque assist (M mode in MOSFET driver), the energy flowis from the vehicle-mounted battery system to the ISG, and in the generation mode (G) in the MOSFET driver, the energy flowis between the integrated starter generator (ISG)and the vehicle-mounted battery system.

The sensing assemblymay provide a data that is fed as input to the control unitto detect angles of the piston assembly, count the strokes and identify the four strokes of the 4-stroke engine, or alternatively, the two strokes of the 2-stroke internal combustion (IC) engine.

illustrates a system viewof the control unitfor enabling crankshaft position sensing and motor engagement according to some embodiments herein. The control unitincludes a controller or a processor. The control unitidentifies the crankshaft assemblyposition and the stroke number (identify if it is the suction stroke, the compression stroke, the power stroke, or the exhaust stroke) and, based on conditions of the battery, the control unitswitches the Integrated Starter Generator (ISG)to control the MOSFET bridgethrough interfacesA,N of MOSFET driversto provide the torque-assist during the compression stroke. The sensing assemblyprovides the positional reference of the Top Dead Centre (TDC) and Bottom Dead Centre (BDC) as well as the crank angle.

In some embodiments, the sensing assemblyderives a pulse stream during crankshaft rotation, enabling the control unitto determine the rotational angle at any instance of the crankshaft assembly.

The controller or processorin the control unitimplements the electric torque assist, preferably in the compression stroke, and switch the Integrated Starter Generator (ISG)to the generation mode (G) during the remaining three strokes. The control unitmay determine a decision to switch the ISGto the motoring mode (M) or the generation mode (M) during the one or more engine cycle phases. When an ignition key switchis enabled, an Intergated Starter Generator (ISG) controller powered up by a power supply regulator and a battery voltage sensing circuitprovide information about battery voltage to the controller or processorfor optimum use of battery energy during the motoring mode (M) in the process of switching on electric torque assist and monitoring voltage. The torque-assist is enabled, for example, on engine RPM, and temperature. Electric torque assist duration is a variable parameter that is decided by the controller or processorin the control unit.

The threshold setting for the electric torque assist may be governed by an inertial component that supports a basic level of rotational inertial energy. The inertial energy available is equated as a product of the inertial mass and the square of the rotational velocity. As the speed of the engine increases, the inertial energy moves upwards as the square of the product of the engine speed, and the need for electric torque assist disappears, and the controller or processorenables the generation (G) mode.

In some embodiments, the system viewimplements the electric torque assist to compensate the lower inertia in the IC engine. A collection of interface elements) monitors the battery voltage through the battery voltage sensingcircuit. The power supply regulator powers the control unitand the ignition starts to switch to turn on the vehicle. A wiring connectionconnects the MOSFET bridgeand the Integrated Starter Generator (ISG)that carries power during the generation (G) mode and the motoring mode (M) of the Integrated Starter Generator (ISG).

illustrates a graphical representation of improved speed variation during a compression stroke with a reduced inertial component in the Internal Combustion (IC) engine according to some embodiments herein. The graphical representation includes degrees in an X-axis and engine speed in rpm in a Y-axis. The graphical representation tracks the speed of the crankshaft during 10 continuous revolutions (i.e. 20 strokes) and five compression and five power strokes in this period for a 4-stroke engine. Plotis a plot for a conventional 4-stroke engine with the normal inertial mass and a regular rich mixture (air to fuel ratio at idling being 14.7) burned in the starting and idling crankshaft speed of near 900 rpm. Plotshows the engine performance with reduced inertia, and it is evident that the average speed drops and the plotare well below the plot. The average rpm has dropped by nearly 100 rpm. As well as the peak to valley shift in the instantaneous speed, with speed dropping from 1200 rpm after the power stroke to 700 rpm as the piston hits the Top Dead Centre (TDC) at the end of the compression stroke, the compression stroke having used a large part of the stored inertial energy is essentially much lower due to the reduced inertial mass. The trace with the assist allows the engine to operate with an air-to-fuel ratio (AFR) of near 13 instead of 14.7, thereby improving emissions.

A traceshows a performance with the electric torque assist. The tracepulls the curve back from its position in the plotto the plot, clearly demonstrating a benefit of the electric torque assist in compensating for the reduced inertia during the compression stroke. The electric torque assist optimizes the speed between the peak speed at the end of the compression stroke when the Bottom Dead Centre (BDC) is reached and the valley of the lowest speed when the Top Dead Centre (TDC) is reached at the end of the compression stroke with the electric torque assist.

illustrates a switching sequence of the Integrated Starter Generator (ISG)to the motoring mode (M) when the compression stroke is identified and a current shifting in the Integrated Starter Generator (ISG)due to a mode change from the generation (G) mode to the motoring mode (M) according to some embodiments herein. The current switching sequenceof the Integrated Starter Generator (ISG)during the torque-assist phase is shown. The fundamental timing clock component to identify the compression stroke, the Top Dead Centre (TDC) and the Bottom Dead Centre (BDC) determination is from a pulse stream. A derivative of this pulse stream is a trace of the Top Dead Centre (TDC) repeating a crank sensor pulseduring the end of the compression stroke and the exhaust stroke. The switch over of the Integrated Starter Generator (ISG) to the electric torque assist is at an instance ofwhen the Bottom Dead Centre (BDC) hits prior to the beginning of the compression stroke. The reversal of the electric torque assist is achieved when the Top Dead Centre (TDC) hits prior to the ignitionof the termination of the compression stroke. The magnitude of the torque-assist compensates for the drop in crankshaft speed due to the lower inertia illustrated by the plateau of a current trace.

illustrates a graphical representation of enhanced emission control of the IC engine with and without the electric torque assistance ofaccording to some embodiments herein. A tracedepicts a performance of the IC engine with the conventional inertial mass loaded without the electric torque assist during this period, that clearly shows that the total hydrocarbon (THC) emitted by the IC engine is high in relation to time and speed. A tracedepicts a performance of the IC engine with the electric torque assist that has less inertial mass than a conventional inertial mass-loaded IC engine, while the THC emitted by the IC engine is reduced when compared to the IC engine without the electric torque assist throughout this period.

are flow diagrams that illustrates a method for employing the Integrated Starter Generator (ISG)for electric torque assistance in the Internal Combustion (IC) engine according to some embodiments herein. At a stepa stream of pulses proportional to the instantaneous speed of the crankshaft assemblyand the position of the piston assembly reaching a TDC (top dead center) of the IC engine when it is running is provided using the sensing assembly. At a step, the instantaneous speed of the crankshaft assemblyis determined using the stream of pulses from the sensing assemblyusing the control unit. At a step, the pulses from the sensing assemblyare computed into one or more engine cycle phases including the suction stroke, the compression stroke, the power stroke, and the exhaust stroke using the control unit. At a step, the instanteous speed of the crankshaft assemblyand speed shortfall in the IC engine is monitored using the control unit. At a step, the target value for the torque-assist is determined by analysing the speed shortfall and the instantaneous speed of the crankshaft assembly, or the position of piston assembly is detected by the sensing assembly, using the control unit.

At a step, the torque-assist is provided to the ISGby switching the MOSFET bridgeto the motoring mode (M) using the MOSFET driverto maintain the optimum electric torque assist throughout the one or more engine cycle phases using the control unit. At a step, the ISGis switched to the generation mode (G) using the MOSFET bridgewhen the instantaneous speed of the crankshaft assemblyis greater than or equal to the predefined threshold speed value of the IC engine.

The aforementioned description of the specific embodiments will sufficiently reveal the various aspects of the embodiments herein that others can readily modify and/or adapt such specific embodiments for various applications using current knowledge, and thus such adaptations and modifications should and are intended to be understood within the meaning and range of equivalents of the disclosed embodiments. It should be understood that the phraseology or terminology used herein is intended to describe rather than limit. While the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments can be modified within the spirit and scope of the appended claims.